1. Field of the Invention
This invention relates generally to serial busses and, more specifically, to a method for allowing multiple access to the serial bus by a plurality of circuit boards.
2. Description of the Prior Art
Popular serial communication protocols in current usage have two methods of addressing individual boards in a system: (1) Individual Chip Select, and (2) Software Addressing. Both of the above methods have potential down sides. When using an individual chip select method, every board on the serial bus is directly connected to an individual chip select line. This creates a high burden in terms of board area devoted to the individual chip select lines. This burden goes up as the number of boards on the bus increases. When using software addressing, there is a limited number of bits (i.e., three) that are reserved for addressing individual boards. This limits the total number of circuit boards that may exist on the same bus to eight. Both of the above methods also have the limitation that all the addressing must be set and in place at the time the system is designed. This prohibits designing a flexible system where circuit boards may be swapped within the system.
Therefore, a need existed to provide an improved method for allowing identification of circuit boards in a system. The method must allow for identification of circuit boards in systems having only a few to an infinite number of circuit boards. The method will allow for flexible multiple access to a serial bus by a plurality of circuit boards. The method will also allow for easy hot plugging of circuit boards on the serial bus.